In the context of mailpiece delivery, a “self-mailer” is a term used to define mailpieces which employ some portion of its content information or material to form a finished mailpiece, i.e., a mailpiece ready for delivery. In addition to certain efficiencies gained from the dual use of paper stock, i.e., as both envelope and content material, self-mailers mitigate the potential for disassociation of content material from the mailing envelope, i.e., preventing mail from being delivered to an incorrect address.
One example of a self-mailer includes a sheet of content material which has been folded, e.g., a bi- or tri-fold brochure or pamphlet and sealed along a free edge such that the destination address/postage may be printed on, or applied to, a backside surface of the content material. As such, the folded sheet functions dually as both an envelope for mailing purposes and as the substrate for conveying printed content/information.
The various postal services e.g., United States Postal Service (USPS) and Royal Mail, often impose certain criteria in connection with the creation of self-mailers to ensure that the folded sheets remain secure while being handled/processed by automated postal equipment, e.g., sorters, facers, cancellers, etc. One regularly accepted and historically reliable means for securing a self-mailer include the use of adhesive tabs folded over or extending across a free edge of the folded sheets. Generally, one or two tabs are adequate to secure the folded sheets at the center, or at each end thereof, to capture the free edges.
Conventional devices or systems for creating folded self-mailers typically include a folding station, a tabbing apparatus and a conveyor/stacker. The folding station accepts one or more sheets of printed content material and folds the sheet in a bi- or tri-fold, gate-fold or Z-fold configuration. The folded sheet is then fed to the tabbing apparatus where adhesive tabs are dispensed from a carrier substrate for precise placement along at least one free edge of the folded sheet. Generally, the tabbing apparatus can be configured to perform two types of tabbing operations. In one mode of operation, the tabbing apparatus is configured to perform “edge tabbing” wherein one or more tabs are folded over an edge of the sheets, i.e., into equal halves such that half of each tab secures a folded edge of the sheet(s). In another mode of operation, the tabbing apparatus is configured to perform “surface tabbing” wherein the tab or tabs are laid flat to secure the free edge of the folded sheet(s). That is, due to the manner in which the sheets are folded, the free edge of the folded sheet(s) is not disposed along an edge of the self-mailer, but rather located at a more central location, e.g., a gate-fold. As such, the tabs are not folded over along an edge of the self-mailer, but placed and pressed flat to secure a backside surface of a folded sheet together with a free edge thereof. Thereafter, the finished self-mailers are fed to a conveyor/stacker and stacked for subsequent traying operations.
While these apparatus/systems have successfully served the needs of large volume, mail service providers, several difficulties have persisted, particularly with respect to the efficacy of the fold line produced by the folding apparatus. Particularly problematic is sheet material which employ “cross-folds” wherein a subsequent fold line crosses over an initial or previously generated fold line, e.g., a subsequent fold line which is orthogonal to the initial cross-fold. These cross-folds become more difficult to produce when employing relatively stiff and/or thick sheet material such as may be used to fabricate high-quality marketing materials/literature. That is, due to the stiffness and/or thickness of the sheet material, the cross-fold can produce wrinkles which degrade the aesthetic appearance of the folded sheet material. Alternatively, the cross-fold can produce a local thickness concentration at the intersection of the fold lines and adversely impact the ability to retain the fold configuration of the sheet material.
In an effort to facilitate folding and/or closure of the sheet material about a cross-fold, one of two methods/systems is typically adopted. A first technique employs a conventional system of rollers which apply a high compaction pressure at the nip of the rollers to mitigate wrinkles and forcibly retain the fold configuration. Alternatively, the line about which the cross-fold will be produced is scored, i.e., severing fibers through a portion of the sheet material thickness, to facilitate subsequent folding operations. With respect to the use of compaction rollers, the nip between the rollers must be highly controlled, and as such, difficulties are encountered when folding sheet collations or sheet material which varies in thickness. With respect to scoring the sheet material, severing fibers can introduce stress concentrations at the fold line and the potential to tear the sheet material at the cross-fold. Furthermore, the induced stress concentrations can lead to premature failure of the fold line, i.e., causing the sheet material to tear following a relatively small number of cycles. Moreover, the scoring apparatus must be highly controlled to avoid cutting through the sheet material and introduces added complexity/cost to the folding apparatus.
A need, therefore, exists for a system and method for cross-folding sheet material which is reliable, does not require precise operation/control, and minimizes complexity/cost.